Add Multi-Instance Support for Unity MCP

MCPForUnity/Editor/Helpers/PortManager.cs

@@ -60,14 +60,17 @@ public static int GetPortWithFallback()
                     if (IsDebugEnabled()) Debug.Log($"<b><color=#2EA3FF>MCP-FOR-UNITY</color></b>: Stored port {storedConfig.unity_port} became available after short wait");
                     return storedConfig.unity_port;
                 }
-                // Prefer sticking to the same port; let the caller handle bind retries/fallbacks
-                return storedConfig.unity_port;
+                // Port is still busy after waiting - find a new available port instead
+                if (IsDebugEnabled()) Debug.Log($"<b><color=#2EA3FF>MCP-FOR-UNITY</color></b>: Stored port {storedConfig.unity_port} is occupied by another instance, finding alternative...");
+                int newPort = FindAvailablePort();
+                SavePort(newPort);
+                return newPort;
             }
 
             // If no valid stored port, find a new one and save it
-            int newPort = FindAvailablePort();
-            SavePort(newPort);
-            return newPort;
+            int foundPort = FindAvailablePort();
+            SavePort(foundPort);
+            return foundPort;
         }
 
         /// <summary>

MCPForUnity/Editor/MCPForUnityBridge.cs

@@ -362,7 +362,22 @@ public static void Start()
                         }
                         catch (SocketException se) when (se.SocketErrorCode == SocketError.AddressAlreadyInUse && attempt >= maxImmediateRetries)
                         {
+                            // Port is occupied by another instance, get a new available port
+                            int oldPort = currentUnityPort;
                             currentUnityPort = PortManager.GetPortWithFallback();
+
+                            // Safety check: ensure we got a different port
+                            if (currentUnityPort == oldPort)
+                            {
+                                McpLog.Error($"Port {oldPort} is occupied and no alternative port available");
+                                throw;
+                            }
+
+                            if (IsDebugEnabled())
+                            {
+                                McpLog.Info($"Port {oldPort} occupied, switching to port {currentUnityPort}");
+                            }
+
                             listener = new TcpListener(IPAddress.Loopback, currentUnityPort);
                             listener.Server.SetSocketOption(
                                 SocketOptionLevel.Socket,
@@ -474,6 +489,22 @@ public static void Stop()
             try { AssemblyReloadEvents.afterAssemblyReload -= OnAfterAssemblyReload; } catch { }
             try { EditorApplication.quitting -= Stop; } catch { }
 
+            // Clean up status file when Unity stops
+            try
+            {
+                string statusDir = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".unity-mcp");
+                string statusFile = Path.Combine(statusDir, $"unity-mcp-status-{ComputeProjectHash(Application.dataPath)}.json");
+                if (File.Exists(statusFile))
+                {
+                    File.Delete(statusFile);
+                    if (IsDebugEnabled()) McpLog.Info($"Deleted status file: {statusFile}");
+                }
+            }
+            catch (Exception ex)
+            {
+                if (IsDebugEnabled()) McpLog.Warn($"Failed to delete status file: {ex.Message}");
+            }
+
             if (IsDebugEnabled()) McpLog.Info("MCPForUnityBridge stopped.");
         }
 
@@ -1184,13 +1215,38 @@ private static void WriteHeartbeat(bool reloading, string reason = null)
                 }
                 Directory.CreateDirectory(dir);
                 string filePath = Path.Combine(dir, $"unity-mcp-status-{ComputeProjectHash(Application.dataPath)}.json");
+
+                // Extract project name from path
+                string projectName = "Unknown";
+                try
+                {
+                    string projectPath = Application.dataPath;
+                    if (!string.IsNullOrEmpty(projectPath))
+                    {
+                        // Remove trailing /Assets or \Assets
+                        projectPath = projectPath.TrimEnd('/', '\\');
+                        if (projectPath.EndsWith("Assets", StringComparison.OrdinalIgnoreCase))
+                        {
+                            projectPath = projectPath.Substring(0, projectPath.Length - 6).TrimEnd('/', '\\');
+                        }
+                        projectName = Path.GetFileName(projectPath);
+                        if (string.IsNullOrEmpty(projectName))
+                        {
+                            projectName = "Unknown";
+                        }
+                    }
+                }
+                catch { }
+
                 var payload = new
                 {
                     unity_port = currentUnityPort,
                     reloading,
                     reason = reason ?? (reloading ? "reloading" : "ready"),
                     seq = heartbeatSeq,
                     project_path = Application.dataPath,
+                    project_name = projectName,
+                    unity_version = Application.unityVersion,
                     last_heartbeat = DateTime.UtcNow.ToString("O")
                 };
                 File.WriteAllText(filePath, JsonConvert.SerializeObject(payload), new System.Text.UTF8Encoding(false));

MCPForUnity/UnityMcpServer~/src/models.py

@@ -1,4 +1,5 @@
 from typing import Any
+from datetime import datetime
 from pydantic import BaseModel
 
 
@@ -7,3 +8,28 @@ class MCPResponse(BaseModel):
     message: str | None = None
     error: str | None = None
     data: Any | None = None
+
+
+class UnityInstanceInfo(BaseModel):
+    """Information about a Unity Editor instance"""
+    id: str  # "ProjectName@hash" or fallback to hash
+    name: str  # Project name extracted from path
+    path: str  # Full project path (Assets folder)
+    hash: str  # 8-char hash of project path
+    port: int  # TCP port
+    status: str  # "running", "reloading", "offline"
+    last_heartbeat: datetime | None = None
+    unity_version: str | None = None
+
+    def to_dict(self) -> dict[str, Any]:
+        """Convert to dictionary for JSON serialization"""
+        return {
+            "id": self.id,
+            "name": self.name,
+            "path": self.path,
+            "hash": self.hash,
+            "port": self.port,
+            "status": self.status,
+            "last_heartbeat": self.last_heartbeat.isoformat() if self.last_heartbeat else None,
+            "unity_version": self.unity_version
+        }

MCPForUnity/UnityMcpServer~/src/port_discovery.py

@@ -14,10 +14,15 @@
 import glob
 import json
 import logging
+import os
+import struct
+from datetime import datetime
 from pathlib import Path
 import socket
 from typing import Optional, List
 
+from models import UnityInstanceInfo
+
 logger = logging.getLogger("mcp-for-unity-server")
 
 
@@ -56,22 +61,43 @@ def list_candidate_files() -> List[Path]:
     @staticmethod
     def _try_probe_unity_mcp(port: int) -> bool:
         """Quickly check if a MCP for Unity listener is on this port.
-        Tries a short TCP connect, sends 'ping', expects Unity bridge welcome message.
+        Uses Unity's framed protocol: receives handshake, sends framed ping, expects framed pong.
         """
         try:
             with socket.create_connection(("127.0.0.1", port), PortDiscovery.CONNECT_TIMEOUT) as s:
                 s.settimeout(PortDiscovery.CONNECT_TIMEOUT)
                 try:
-                    s.sendall(b"ping")
-                    data = s.recv(512)
-                    # Check for Unity bridge welcome message format
-                    if data and (b"WELCOME UNITY-MCP" in data or b'"message":"pong"' in data):
-                        return True
-                except Exception:
+                    # 1. Receive handshake from Unity
+                    handshake = s.recv(512)
+                    if not handshake or b"FRAMING=1" not in handshake:
+                        # Try legacy mode as fallback
+                        s.sendall(b"ping")
+                        data = s.recv(512)
+                        return data and b'"message":"pong"' in data
+
+                    # 2. Send framed ping command
+                    # Frame format: 8-byte length header (big-endian uint64) + payload
+                    payload = b"ping"
+                    header = struct.pack('>Q', len(payload))
+                    s.sendall(header + payload)
+
+                    # 3. Receive framed response
+                    response_header = s.recv(8)
+                    if len(response_header) != 8:
+                        return False
+
+                    response_length = struct.unpack('>Q', response_header)[0]
+                    if response_length > 10000:  # Sanity check
+                        return False
+
+                    response = s.recv(response_length)
+                    return b'"message":"pong"' in response
+                except Exception as e:
+                    logger.debug(f"Port probe failed for {port}: {e}")
                     return False
-        except Exception:
+        except Exception as e:
+            logger.debug(f"Connection failed for port {port}: {e}")
             return False
-        return False
 
     @staticmethod
     def _read_latest_status() -> Optional[dict]:
@@ -158,3 +184,94 @@ def get_port_config() -> Optional[dict]:
                 logger.warning(
                     f"Could not read port configuration {path}: {e}")
         return None
+
+    @staticmethod
+    def _extract_project_name(project_path: str) -> str:
+        """Extract project name from Assets path.
+
+        Examples:
+            /Users/sakura/Projects/MyGame/Assets -> MyGame
+            C:\\Projects\\TestProject\\Assets -> TestProject
+        """
+        if not project_path:
+            return "Unknown"
+
+        try:
+            # Remove trailing /Assets or \Assets
+            path = project_path.rstrip('/\\')
+            if path.endswith('Assets'):
+                path = path[:-6].rstrip('/\\')
+
+            # Get the last directory name
+            name = os.path.basename(path)
+            return name if name else "Unknown"
+        except Exception:
+            return "Unknown"
+
+    @staticmethod
+    def discover_all_unity_instances() -> List[UnityInstanceInfo]:
+        """
+        Discover all running Unity Editor instances by scanning status files.
+
+        Returns:
+            List of UnityInstanceInfo objects for all discovered instances
+        """
+        instances = []
+        base = PortDiscovery.get_registry_dir()
+
+        # Scan all status files
+        status_pattern = str(base / "unity-mcp-status-*.json")
+        status_files = glob.glob(status_pattern)
+
+        for status_file_path in status_files:
+            try:
+                with open(status_file_path, 'r') as f:
+                    data = json.load(f)
+
+                # Extract hash from filename: unity-mcp-status-{hash}.json
+                filename = os.path.basename(status_file_path)
+                hash_value = filename.replace('unity-mcp-status-', '').replace('.json', '')
+
+                # Extract information
+                project_path = data.get('project_path', '')
+                project_name = PortDiscovery._extract_project_name(project_path)
+                port = data.get('unity_port')
+                is_reloading = data.get('reloading', False)
+
+                # Parse last_heartbeat
+                last_heartbeat = None
+                heartbeat_str = data.get('last_heartbeat')
+                if heartbeat_str:
+                    try:
+                        last_heartbeat = datetime.fromisoformat(heartbeat_str.replace('Z', '+00:00'))
+                    except Exception:
+                        pass
+
+                # Verify port is actually responding
+                is_alive = PortDiscovery._try_probe_unity_mcp(port) if isinstance(port, int) else False
+
+                if not is_alive:
+                    logger.debug(f"Instance {project_name}@{hash_value} has heartbeat but port {port} not responding")
+                    continue
+
+                # Create instance info
+                instance = UnityInstanceInfo(
+                    id=f"{project_name}@{hash_value}",
+                    name=project_name,
+                    path=project_path,
+                    hash=hash_value,
+                    port=port,
+                    status="reloading" if is_reloading else "running",
+                    last_heartbeat=last_heartbeat,
+                    unity_version=data.get('unity_version')  # May not be available in current version
+                )
+
+                instances.append(instance)
+                logger.debug(f"Discovered Unity instance: {instance.id} on port {instance.port}")
+
+            except Exception as e:
+                logger.debug(f"Failed to parse status file {status_file_path}: {e}")
+                continue
+
+        logger.info(f"Discovered {len(instances)} Unity instances")
+        return instances

MCPForUnity/UnityMcpServer~/src/pyproject.toml

@@ -6,7 +6,7 @@ readme = "README.md"
 requires-python = ">=3.11"
 dependencies = [
  "httpx>=0.27.2",
- "fastmcp>=2.12.5",
+ "fastmcp>=2.13.0",
  "mcp>=1.16.0",
  "pydantic>=2.12.0",
  "tomli>=2.3.0",